# Food Processing Unit Operations Questions and Answers – Distillation – Partial Pressure

This set of Food Processing Unit Operations Multiple Choice Questions & Answers focuses on “Distillation – Partial Pressure”.

1. How to calculate partial pressure?
a) Sum of the pressures of each individual gas
b) Total pressure multiplied by the mole fraction of that gas
c) Sum of the mole fraction of each individual gas
d) Total concentration multiplied by the mole fraction of that gas

Explanation: The total pressure of the mixture of gases is the sum of the individual pressures of each gas. The partial pressure of an individual gas is equivalent to the total pressure multiplied by mole fraction of that individual gas.

2. What is the use of partial pressure?
a) To predict the movement of gases
b) To predict the concentration change
c) To predict the pressure change
d) To predict the mole fraction

Explanation: Partial pressure is the force exerted by a gas. Partial pressure is very important in predicting the movement of gases.

3. What is partial pressure of water vapor?
a) 23.8 mm Hg
b) 230.8 mm Hg
c) 2.38 mm Hg
d) 0.238 mm Hg

Explanation: The water vapor pressure is the partial pressure of water vapor in any gas mixture in equilibrium with solid or liquid water.

4. What is r value in pV= nRT?
a) 0.8314 J/mol•K
b) 831.4 J/mol•K
c) 83.14 J/mol•K
d) 8.314 J/mol•K

Explanation: The ideal gas law is pV = nRT, where n is the number of moles, and R is universal gas constant. The value of R depends on the units involved, and S.I. unit is 8.314 J/mol•K.

5. Which of the following component is constant in Boyle’s law?
a) Concentration
b) Pressure
c) Temperature
d) Volume

Explanation: At constant temperature, the volume of a given mass of a dry gas is indirectly proportional to its pressure is known as Boyle’s law.

6. Does partial pressure depend on temperature?
a) True
b) False

Explanation: As temperature increases the molecular activity at the surface of the water also increases. An increase in temperature would increase the partial pressure where the volume of the container remains constant.

7. What is the limitation of Dalton’s law?
a) It implies only for real gases at low pressure
b) It implies only for real gases at high pressure
c) It implies only for real gases at low concentration
d) It implies only for real gases at high concentration

Explanation: The Dalton’s law is good for real gases at low pressure, but at high pressure, it deviates considerably. The mixture of gases is non-reactive in nature. Another assumption is that the interaction between each individual gas molecules is same as the molecules in the mixture.

8. Which of the following statements about partial pressure are correct?
Statement 1: The partial pressure of each gas in a mixture is not proportional to its mole fraction..
Statement 2: The partial pressure of each gas is the product of the total pressure and the mole fraction of that gas.
a) True, False
b) True, True
c) False, True
d) False, False

Explanation: The partial pressure of each gas in a mix is proportional to its mole fraction. The pressure exerted by each gas in a gas mix is not dependent on the pressure exerted by all other gases present. Partial pressure of each gas is the product of the mole fraction and total pressure of that gas.

9. In an experiment,the barometric pressure of gas is 1.043 atm, Some H2 was collected over water at 27.0°C. What is the partial pressure of the dry H2 in the container?
a) 0.1021 atm
b) 102.1 atm
c) 10.21 atm
d) 1.021 atm

Explanation:
PTotal = 1.056atm
PH2O(at 27°C) = 0.035 atm
Therefore, PTotal = PH2O + PH2
PH2 = PT − PH2O
PH2 = 1.056 atm – 0.035 atm = 1.021 atm

10. The pressure of a 2.74moles of a gas in a container was 432.0 torr. What would the pressure inside the container be if 5.05 moles of the gas was in it?
a) 896.20 torr
b) 796.20 torr
c) 596.20 torr
d) 696.20 torr

Explanation:
n1 = 2.74 mol P1 = 432.0torr
n2 = 5.05mol P2 =?
Therefore, according to Dalton’s law,
P1/n1=P2/n2
P2 = P1n2/n1
= (432.0 torr)(5.05mol)/2.74mol
= 796.20torr

Sanfoundry Global Education & Learning Series – Food Processing Unit Operations.

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